Jean

Guys, we cannot thank you enough for all this data , there is so much to learn in here that it will take us a good couple of weeks to dissecate it all.

I am working on the coast-down and CD calculations, hopefully by tomorrow I can give a number.

That 9M intercooler does seem to work well, I wish we had some similar data from the likes of Blown 6 and Protomotive to compare and test as well, maybe in the near future.

TB, 100-300kph in about 25s is about as fast as the 996TT and 997TT with 700PS that we are seeing out there, despite the poor aerodynamics on your car that we have calculated. BTW, I am sure that "Schmirler" will appreciate immensely this data.

to all, thanks!

EDIT: Felix, if you could replace the graphs posted in a bit smaller format and removing the lateral Gs line it would help the reading a lot. Another suggestion is to smoothen the temp and long Gs to 0.1s or 0.2s, it will be more meaningful as it will eliminate the spikes. Sorry to be such a PITA

Jussi

Also many thanks from these IC tests !
I need them because I'm still running stock IC and searching good upgrade choice.. so it might be that 9M..

TB993tt

I am eagerly awaiting aerodynamic data which Jean is crunching from a coastdown run which I did from 275kph (170mph) , he has a coastdown run from Phelix as a benchmark for a stock 993tt bodyshape (turbo S).

It will also be interesting what Cd/CdA Phelix's car calculates to using a smooth surface coefficient in the calculation - It will probably show worse the the Cd0.34/CdA 0.656 of the standard car and this should enable us to reverse calculate just how bad the surface friction is at Bruntingthorpe and allow a calculation of a 0-300kph based on a smooth flat surface

A revelation to me is that it is CdA which we have to look at rather than Cd alone....
MOD timed his stock bodied 993tt 0-300kph equivalent to ~36s which is the same as the 997GT2 - MOD has engine dyno 533PS so identical to the 997GT2

When we look at relative Cds MODs 993tt = Cd0.34 997 GT2 = Cd0.32 but then we look at CdAs
MOD 993tt CdA = 0.656 997GT2 CdA = 0.66

This tells the story.....

TB993tt

Brakes looked like new before this session - now look at them !

Does the dark patching go away ?

MOD500

The blue patches will go away with sedate road use ..... mine were blue after the micro v-max, but are 'clean' again after 200 miles of road driving yesterday

TB993tt

Just to wrap this thread up, the comparison between the Frankenstein Front spoiler and the current FVD GT2 lip is illustrated below (apologies for the dodgy xls but I don't know how to overlay in Driftbox ?) the car was 4 seconds faster 0-300kph and did it 320 metres earlier !

I have recently had a service including all valve clearances being readjusted (the tech said they were all very tuight and he couldn't get his smallest feeler gauge in there) and new plugs so the engine was in top fettle and did feel strong.

It is very difficult to judge since one does get used to these speeds but I would say that the car feels less stable now than with the "Franky" front end at 300kph, and also the stability at the front is noticably worse as the fuel runs dry and the weight goes off the front. Next time I am going to lower the front a bit more to go more nose down to see what if any difference it makes.

MOD said that following me down the strip the rear of the car was moving around quite noticably at the high speed

Jean

I am not sure whether this was posted earlier but I find it interesting that the 3.4 ltr. 930S that was built by Ofzsky and Reinhold Schmirler (the fathers of the Yellowbird in fact) , tested back in 1989 and posted in the Guinness Book of records for reaching 348kph, did the 0-300kph in 29.8s. It also had 580bhp at 1.3 Bar

Now the question that comes to mind.... With quite poor aerodynamics, small 265/40x17 wheels and tires, no Secan intercooler, how did this car manage to reach the same acceleration up to 300kph 18 years earlier.

Weight has something to do certainly, but still, quite surprising!

TB993tt

Jean
It must be combination of weight and aerodynamics, it has the sloped screen conversion and is gutterless and smoother front spoiler so the 930s CDA of 0.725 must have been improved upon....

Mine was 3s faster 0-250kph despite weighing ~200+kg more and 4WD (probably due to a fatter power curve) but then as the drag loaded up this car did 250-300kph in 9.38s where mine took 11.94s...

This same early engine configuration ended up at 780hp using the same basic set up, the intercoolers were big full width Behr offerings - They used some early form of Motronic (like on the CTR) pressure sensing which did include knock sensors - RS rarely breach 700hp level with any of the engines they have done since these monsters in the late 80's, early 90s I think this is because they have found out the level at which the power takes its toll and expensive engine rebuilds become too common....

Someone else mentioned it on the other thread about how rich these early pressure sensing Motronic engines ran, my CTR managed about 10mpg and always reaked of fuel -could it be they (inc RS) used this to help compensate for the mediocre intercooling ?

Richard mentions it in the other thread about the main benefit of keeping the IAT down being lowered other tepms like EGT head temp etc -my guess is that these early 780hp RS units with old tech intercoolers had prett short lives before expensive tear downs - new heads/barrels/pistons etc.....

Like you I am really looking forward to Jussi's aero optimised special setting a fast 0-300kph, with the aero changes he has made it is going to be ground breaking.

TB993tt

I am still a inquisitive as to what role the airstrip at Bruntingthorpe plays in slowing down acceleration relative to other venues. It has the slope of 5m for the first mile and the surface is particularly nasty. I have put a couple of pics below so those who have not been can get a taster - It is a rough finish tarmac/asphalt () which is littered with bitumen repair strips which stand proud of the surface (second pic attempts to show this)
Driving over it makes a racket and it contibutes to the lateral stability (or lack thereof) at high speed





I haven't got much data in current configuration but I have a 60-139mph done on a regular strip of tarmac, slight downhill but negligable, it took 8.74s.

I have looked at 5 runs at Bruntingthorpe when the fuel load (and passenger) load would be comparable and the 60-139mph takes ~9.8s

So how much faster would my 0-300kph be on some kinder flatter tarmac ?

935racer

When is the next run? If you guys like I will bring my car along. I'll wager it will be quick to about 170 mph but then it just stops! It has the aerodynamics of a barn door and even if I back all the wings off I doubt it will make a lot more than 180. I would be really intersted to see your cars run, especially as I have a bit of inside information! Should make a good day out.
Richard.

Jussi

I agree that fully and also those smaller=lighter wheels and little narrower rubbers help.
That under 30 sec to 300kph acceleration must be felt very frightening at those days !

Maybe with better IC that time would have been even 2 seconds faster.

Toby:
My aerodynamics mods are going forward little by little because I don't have time much to spend with it.
But now I'm finalizing headlight fittings and doing frames for lower parts of lights that I can install sealing rubber around it
Actually rain gutters delete was quite easy and straightforward jobs compared to that headlight conversion and aero screen.
I have to also do another glass support for upper frame (roof line) because I want that glass will be at same level than roof line. Original frame is located too deep (3cm). It must be about 1cm for glass adhesive.

Felix

Strange acceleration curve - steeper as the speed climbs!

Jussi

Maybe driver did soft-start and pressed pedal carefully and just at 200kph did WOT acceleration

TB993tt

It is just the way the scaling is, here's mine in the same graph:

Jean

TB I agree with your analysis, interesting when one breaks it down to sectors, aerodynamics did seem to play a big role. Looks like their own CTR yellowbird philosophy pays well, this was a direct attempt by these two gentlemen at targeting the RUF record using like for like engineering, and they succeeded.

I heard from different sources that this engine had 962 IMSA heads. On this picture it looks like an engine with twin plugs and with the intercooler that looks like a OEM BEHR as you mentioned, with custom end tanks, and that these two gentlemen used for their 80' and early 90s monster creations.


And this one is for Jussi. Check this beauty, who needs lightweight Mov its?